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Turbine flow meters have long been a preferred technology for obtaining precise measurements of fluid flow in the aerospace industry. In addition to their high accuracy, they are recognized for exceptional turndown, repeatability and speed of response.

With recent design enhancements, instrumentation manufacturers have expanded the advantages turbine flow meters offer in a host of demanding aerospace applications. Indeed, the turbine remains one of the most accurate and reliable transducers for today's critical flow measurements.

In the aerospace and defense industry, testing of fuel system components is key to ensuring final vehicle or aircraft performance. By pairing a flow meter with a flow computer or smart transmitter, aerospace equipment manufacturers can perform precise metering of fuel flow in engine test cells.

Experience has shown that turbine flow meters are the sensor-of-choice for test and measurement applications requiring the best accuracy available with the benefits of high resolution, extended turndown across wide flow ranges, fast speed of response, proven reliability, and compact size. These meters also feature a small footprint for ease of installation on both fixed and portable test stands.

Turbine flow meters incorporate a time-tested measuring principle. They contain a freely suspended rotor, and the flow against its vanes causes the device to rotate at a rate proportional to flow velocity. A sensor/transmitter is used to detect the rotational rate of the rotor; when the fluid moves faster, more pulses are generated. The transmitter processes the pulse signal to determine the flow of the fluid in either forward or reverse direction.

Common Flow Applications

Available in compact and lightweight packages with rugged materials of construction, turbine flow meters are used to measure diverse fluids ranging from aircraft fuel to hydraulic fluid, lubricant, cryogenic fluid and coolant.

Common turbine meter applications include:

  • Fuel management

  • Fuel ballast

  • Flight testing

  • Hydraulic system verification

  • Product R&D

  • Qualification and acceptance testing

  • Performance evaluation

  • Maintenance, Repair, and Overhaul (MRO)

From monitoring the fuel consumption of rotary and fixed wing aircraft, missiles and drones, to evaluating the performance of hydraulic fluid and lubricants on test stands, aerospace applications place high demands on flow sensing.

Latest Technology Advancements

In recent years, instrumentation manufacturers have expanded the traditional advantages offered by turbine flow meter technology. Turbine meters now have unprecedented mechanical linearity, resulting in minimizing, or negating, temperature-induced viscosity influence. Meters equipped with sophisticated electronics also provide total compensation to enhance measurement accuracy, while extending linearity over their repeatable range.

The following improvements enable turbine meters to satisfy application requirements in ways once considered infeasible:

  • Dual-rotor designs

  • Hydraulically coupled rotors

  • Helical rotors

  • Embedded processors

  • Ceramic bearings

  • Secured internals

With the latest advancements in technology, turbine flow meter accuracy has improved. Increased sensitivity allows for the precise measurement of even extremely low flow rates in some models. Manufacturers also continue to develop blade and rotor materials that are highly sensitive, durable and less vulnerable to drag and other factors that have traditionally decreased accuracy.

Important Application Considerations

Today's versatile turbine flow meter systems can be configured to achieve the best solution to measure liquid or gas in the most challenging environments. For instance, flow meter suppliers provide an assortment of electrical pickoffs to meet temperature and signal transmission distance requirements, which are complemented by an assortment of electronic processors and indicators. And, selecting from either standard or custom end connection designs can optimize meter installation.

For users with demanding fuel system measurement requirements, the following application consideration guidelines will make turbine flow meter configuration simple, while presenting alternatives to maximize accuracy and minimize cost.

Fluid Parameters: Fluid properties vary from one flow measurement application to another and need to be defined in order to properly develop the correct meter configuration and calibration specification. Fluid parameters include:

  1. Fluid Type

    • Affects the flow meter's wetted parts

    • Defines filtration requirements

    • Determines water, solvent or oil blending calibration

    • Provides fluid density information, required for inferred mass flow

  2. Operating Fluid Temperature (minimum and maximum)

    • Defines fluid viscosity range

    • Identifies the number of calibrations required to develop a Universal Viscosity Curve (UVC) calibration

    • Required to select pickoff type (from cryogenic to high-temperature applications)

    • Determines if remote electronics are required

  3. Static Line Pressure

    • Over 1000 psig changes viscosity and density properties

  4. Flow Range

    • Determines the permissible range in combination with the pressure drop and UVC capability

Meter Type: There are different types of turbine flow meters, and some are more specialized to certain applications. Depending on the particular needs, one style of meter may be preferable to another. Users can choose from four basic configurations, depending on their requirements:

  • Low-flow axial meters

  • Precision single-rotor meters

  • Dual-rotor meters

  • Original Equipment Manufacturer (OEM) specialty meters

Electrical Pickoffs: Because test and measurement applications vary so greatly, most turbine flow meter manufacturers offer multiple electrical pickoff choices to meet specific end user requirements. A pickoff is mounted on the meter body and is used to take the output of the device.